Bug 4960 is about improving accessibility of the site, particularly in long comment threads. It may involve a little rummaging with S2, but while it's not quite a one-line fix it should be pretty easy (testing will likely take longer than coding!), and it will have a big impact on usability.

I'm going to add it to the "doing the two-step" section of the beginners' bugs masterlist, but I felt like this one deserved its own post as well. :-)

Claim it on Bugzilla to make it your own, then show up in IRC or PM me if you'd like cheerleading/guidance/etc!